The "Mini Ice Age" and the solar minimum

Following Facebook I have been vaguely aware of claims in the tabloid press about a new ice age starting in the 2030's. I have not bothered to follow it because even if it were true I would suggest that by 2030 human civilisation (if not the species itself) will be toast.

Here is the response from Guy McPherson:

"This shit about the mini ice age is so fucking ignorant and stupid it hurts. I'll address it for about the twentieth time today. And the last, if all goes well.

"The clathrate gun has been fired. There is no way the proposed mini ice age will significantly slow the heating.

"Every report I've read about this study misquotes it. Solar *magnetic* activity was evaluated. Media reports are claiming solar *intensity* will decline.

"The anticipated 60% reduction in solar magnetic-cycle magnitude translates to a climate forcing of -0.1 W/m2. That's equivalent to a decrease of 8 ppm atmospheric carbon dioxide. The atmosphere currently holds about 400 ppm CO2, with 350 ppm ultimately lethal to humans. Subtracting 8 ppm at this point is analogous to giving a blood transfusion to a dead man."

Speaking for myself, I have fairly successfully insulated myself from the worst of the nutcases.

Here are a couple of reports responding to the reports.

If you want to see the claims you can see them here - 

Earth heading for 'mini ice age' within 15 years

River Thames could freeze over in 2030s when Northern Hemisphere faces bitterly cold winters, scientists say

Media Reports The World Will Enter A ‘Mini Ice Age’ In The 2030s. The Reverse Is True.

Joe Romm

Think Progress,

13 July, 2015

U.K. tabloids, conservative media, and others are (mis)reporting that the Earth will enter a “mini ice age” in the 2030s. In fact, not only is the story wrong, the reverse is actually true.

The Earth is headed toward an imminent speed-up in global warming, as many recent studies have made clear, like this June study by NOAA. Indeed, a March study, entitled “Near-term acceleration in the rate of temperature change,” makes clear that a stunning acceleration in the rate of global warming is around the corner — with Arctic warming rising 1°F per decade by the 2020s!

Also, right now, we appear to be in the midst of a long-awaited jump in global temperatures. Not only was 2014 the hottest year on record, but 2015 is in the process of blowing that record away. On top of that, models say a massive El Niño is growing, as USA Today reported last week. Since El Niños tend to set the record for the hottest years (since the regional warming adds to the underlying global warming trend), if 2015/2016 does see a super El Niño then next year may well crush the record this year sets.

Whatever near-term jump we see in the global temperatures is thus likely to be followed by an accelerating global warming trend — one that would utterly overwhelm any natural variations such as a temporary reduction in solar intensity. 

A recent study concluded that “any reduction in global mean near-surface temperature due to a future decline in solar activity is likely to be a small fraction of projected anthropogenic warming.”

That’s true even for one as big as the Maunder Minimum, which was linked to the so-called Little Ice Age.

The “Little Ice Age” is a term used to cover what appears to have been two or three periods of modest cooling in the northern hemisphere between 1550 and 1850.

I know you are shocked, shocked to learn that unreliable climate stories appear in U.K. tabloids, the conservative media, and those who cite them without actually talking to leading climate scientists. Often there is a half truth underlying such stories, but in this case it is more like a nano-truth.

Last week, in Llandudno, north Wales, the Royal Astronomical Society (RAS) held Cyfarfod Seryddiaeth Cenedlaethol 2015 — the “National Astronomy Meeting 2015″ (in case you don’t speak Welsh). An RAS news release had this startling headline, “Irregular Heartbeat Of The Sun Driven By Double Dynamo.”

Okay, that wasn’t the startling part. This was: “Predictions from the model suggest that solar activity will fall by 60 per cent during the 2030s to conditions last seen during the ‘mini ice age’ that began in 1645.”

CREDIT: WIKIPEDIA

Ah, but the word choice was confusing. We’re not going to have temperature “conditions” last seen during the Little Ice Age. If this one study does turn out to be right, we’d see solar conditions equivalent to the Maunder Minimum in the 2030s.

This won’t cause the world to enter a mini ice age — for three reasons:

• The Little Ice Age turns out to have been quite little.
• What cooling there was probably was driven more by volcanoes than the Maunder Minimum.
• The warming effect from global greenhouse gases will overwhelm any reduction in solar forcing, even more so by the 2030s.
  So how little was the Little Ice Age?
  The most comprehensive reconstruction of the temperature of the past 2000 years done so far, the “PAGES 2k project,” concluded that “there were no globally synchronous multi-decadal hot or cold intervals that define a worldwide Medieval Warm Period or Little Ice Age.”
  
  
  
  Green dots show the 30-year average of the new PAGES 2k reconstruction. The red curve shows the global mean temperature, according HadCRUT4 data from 1850 onwards. In blue is the original hockey stick of Mann, Bradley and Hughes (1999 ) with its uncertainty range (light blue). Graph by Klaus Bitterman.
  
  
  The Little Ice Age was little in duration and in geographic extent. It was an “Age” the way Pluto is a planet.
  
  
  Writing on Climate Progress, climatologist Stefan Rahmstorf noted the researchers “identify some shorter intervals where extremely cold conditions coincide with major volcanic eruptions and/or solar minima (as already known from previous studies).”
  
  
  That brings us to the second point: The latest research finds that what short-term cooling there was during the Little Ice Age was mostly due to volcanoes, not the solar minimum. As “Scientific American” explained in its 2012 piece on the LIA, “New simulations show that several large, closely spaced eruptions (and not decreased solar radiation) could have cooled the Northern Hemisphere enough to spark sea-ice growth and a subsequent feedback loop.” The period associated with the LIA “coincide with two of the most volcanically active half centuries in the past millennium, according to the researchers.”
  
  
  The cooling effect from the drop in solar activity during even a Maunder Minimum is quite modest. Environmental scientist Dana Nuccitelli discussed the literature underscoring that point in a U.K. Guardian post from the summer of 2013, the last time the “Maunder Minimum” issue popped up.
  
  
  That brings us to the third point: Whatever cooling the Little Ice Age saw as result of the Maunder Minimum, it pales in comparison to the warming we are already experiencing — let alone the accelerated warming projected by multiple studies. That’s clear even in Pages 2k reconstruction above.
  Just last month “Nature Communications” published a study called, 
  
  
  “Regional climate impacts of a possible future grand solar minimum.” This found that, “any reduction in global mean near-surface temperature due to a future decline in solar activity is likely to be a small fraction of projected anthropogenic warming.” As with the Little Ice Age, any significant effects are likely to be regional in nature — and, of course, temporary, since a grand solar minimum typically lasts only decades.
  
  
  So, no, the Daily Mail is quite wrong when it trumpets, “Scientists warn the sun will ‘go to sleep’ in 2030 and could cause temperatures to plummet.”
  In actuality, what is going to happen in the business-as-usual emissions scenario (RCP8.5) is closer to the figure below, which plots “rate of change” of warming:
  
  
  
  Global rates of decadal temperature change over 40-year periods. Results are shown for: central climate assumptions (thick solid line), range due to uncertainty in aerosol forcing (grey shading), and range due to uncertainty in climate sensitivity (blue shading). The outer bounding cases are shown as dotted lines. The thin solid black line shows the historical rate of change using the HADCRU4 observational data. The vertical dashed line indicates 2014. Via PNNL.
  
  
  In the RCP8.5 scenario, the rate of warming post-2050 becomes so fast that it is likely to be beyond adaptation for most species — and for humans in many parts of the world, as I discussed here. The warming rate in the central case hits a stunning 1°F per decade. Arctic warming would presumably be at least 2°F per decade. And this goes on for decades.
  
  
  No Maunder Minimum can save homo sapiens from that catastrophic outcome. Only humanity can — by ignoring those who deny or mislead on climate science and instead taking aggressive action to slash carbon pollution ASAP.

This shit about the mini ice age is so fucking ignorant and stupid it hurts. I'll address it for about the twentieth time today. And the last, if all goes well.

The clathrate gun has been fired. There is no way the proposed mini ice age will significantly slow the heating.

Every report I've read about this study misquotes it. Solar *magnetic* activity was evaluated. Media reports are claiming solar *intensity* will decline.

The anticipated 60% reduction in solar magnetic-cycle magnitude translates to a climate forcing of -0.1 W/m2. That's equivalent to a decrease of 8 ppm atmospheric carbon dioxide. The atmosphere currently holds about 400 ppm CO2, with 350 ppm ultimately lethal to humans. Subtracting 8 ppm at this point is analogous to giving a blood transfusion to a dead man.

No, Earth is not heading toward a ‘mini ice age’

By Chelsea Harvey

A solar flare erupts on the sun’s northeastern hemisphere. Media coverage of research into a predicted solar minimum has indicated that Earth is heading toward another “mini ice age.” But climate scientists insist this isn’t the case. (NASA via AP)

Washington Post,

14 July, 2015

This week, warnings of an impending “mini ice age,” set to hit in the 2030s, have been circulating in the media. It’s a story that has caused shivers among the public, but there’s one problem: Climate scientists aren’t buying it.

The ice age idea got rolling last week when researcher Valentina Zharkova, a professor of mathematics at Northumbria University in England, presented some of her recent research into solar variations at the Royal Astronomical Society’s National Astronomy Meeting in Wales. The presentation was based on a study she had published last year in the Astrophysical Journal, which presented a technique for understanding variations in solar radiation and made some predictions about how this radiation will change in the near future. Most notably, the research predicts that between 2030 and 2040, solar activity should drop significantly, leading to a condition known as a “solar minimum.”

[Why the Earth’s past has scientists so worried about sea level rise]

According to the research, solar activity at this time should resemble conditions last seen in the mid-1700s during a period known of low solar radiation known as the “Maunder Minimum.” The interesting thing about this period was that it coincided with a “little ice age” in Europe and North America — a time marked by unusually cold temperatures and bitter winters. Now that Zharkova and her colleagues are predicting another solar minimum coming up, media coverage has jumped on the idea that a modern “mini ice age” is in store.

It’s a dramatic idea, but it isn’t being embraced by many climate scientists, who argue that anthropogenic global warming — brought on by a human outpouring of greenhouse gas emissions into the atmosphere — will far outweigh any climate effects that might be caused by the sun. As far as the solar variations go, “The effect is a drop in the bucket, a barely detectable blip, on the overall warming trajectory we can expect over the next several decades from greenhouse warming,” said Michael Mann, distinguished professor of meteorology at Pennsylvania State University, in an e-mail to The Washington Post.

However, the issue isn’t so simple for Zharkova, who is openly skeptical about the strength of anthropogenic greenhouse gases when compared to the influence of the sun.

On the one hand, Zharkova maintains that her research was not intended to make assumptions about the effects of solar variation on climate — only to lay out predictions about the solar activity itself. “What will happen in the modern Maunder Minimum we do not know yet and can only speculate,” she says. On the other hand, she adds, her gut assumption is that temperatures will drop as they did 370 years ago.

The reason, she says, is her belief that the sun is a bigger influence on earthly climate than the effects of greenhouse gases in the atmosphere. “I am not convinced with the arguments of the group promoting global warming of an anthropogenic nature,” Zharkova says, adding that she would need to examine more research before she could take a clear stance on anthropogenic climate change. Given the right evidence, she says she might accept that human-caused climate change is a bigger factor — but her belief for the time being is that changes in solar radiation are likely to have a bigger influence on temperature changes on Earth, not just during times of solar minimum, but throughout history.

However, this belief is in direct contrast with much literature on the topic. Georg Feulner, deputy chair of the Earth system analysis research domain at the Potsdam Institute on Climate Change Research, co-authored a paper in 2011 specifically examining the effect a solar minimum might have on Earth’s climate. His paper, and subsequent related research has concluded that any solar-related temperature drops would be far outweighed by human-caused global warming. In the case of a solar minimum, such as the one predicted by Zharkova and colleagues, “The expected decrease in global temperature would be 0.1°C at most, compared to about 1.3°C warming since pre-industrial times by the year 2030,” Feulner wrote in an e-mail to the Post.

Complicating the matter further is the idea that the 17th century’s “little ice age” wasn’t even really the result of the solar minimum going on at the time. Feulner also authored another 2011 paper that concluded that volcanic activity was the major cause of a cooler climate during this time, rather than solar variations. The takeaway is that changes in solar radiation are unlikely to hold a candle to the climatic effects being brought about by human-related greenhouse gas emissions.

While Zharkova is one of a small minority of scientists who do not fully accept human activities as the greatest drivers of current climate change, she says she’s surprised at the media response her study has garnered. “I didn’t realize there would be such a strong response from the climate people,” she says, adding that she would need to repeat the calculations of mainstream climate scientists and examine the evidence herself to decide if she can accept their point that anthropogenic influences outweigh those of the sun.

So there may well be a solar minimum in store for the near future — but it’s still probably safe to put your scarves and mittens back in storage for now. Research in the area suggests that greenhouse gas-related warming, not solar variations, will be the dominant climate factor for many years to come.

Still, Zharkova cautions, there’s not much time left until her predicted solar minimum hits. “We have only 15 years to wait, so we’ll learn soon enough,” she says.

Towards an Ice Age?

An ice age? Wouldn't that be ironic!  I don't think I would want to explain this to our Australian cousins right now.

Is our Sun falling silent?

"I've been a solar physicist for 30 years, and I've never seen anything quite like this," says Richard Harrison, head of space physics at the Rutherford Appleton Laboratory in Oxfordshire.

BBC,

21 January, 2014

He shows me recent footage captured by spacecraft that have their sights trained on our star. The Sun is revealed in exquisite detail, but its face is strangely featureless.

"If you want to go back to see when the Sun was this inactive... you've got to go back about 100 years," he says.

This solar lull is baffling scientists, because right now the Sun should be awash with activity.

The Sun's activity may be falling faster than at any time in 10,000 years

It has reached its solar maximum, the point in its 11-year cycle where activity is at a peak.

This giant ball of plasma should be peppered with sunspots, exploding with flares and spewing out huge clouds of charged particles into space in the form of coronal mass ejections.

The Sun should be at the peak of its activity - bursting with flares and coronal mass ejections

But apart from the odd event, like some recent solar flares, it has been very quiet. And this damp squib of a maximum follows a solar minimum - the period when the Sun's activity troughs - that was longer and lower than scientists expected.

"It's completely taken me and many other solar scientists by surprise," says Dr Lucie Green, from University College London's Mullard Space Science Laboratory.

The drop off in activity is happening surprisingly quickly, and scientists are now watching closely to see if it will continue to plummet.

"It could mean a very, very inactive star, it would feel like the Sun is asleep... a very dormant ball of gas at the centre of our Solar System," explains Dr Green.

This, though, would certainly not be the first time this has happened.

During the latter half of the 17th Century, the Sun went through an extremely quiet phase - a period called the Maunder Minimum.

Historical records reveal that sunspots virtually disappeared during this time.

Dr Green says: "There is a very strong hint that the Sun is acting in the same way now as it did in the run-up to the Maunder Minimum."

Mike Lockwood, professor of space environment physics, from the University of Reading, thinks there is a significant chance that the Sun could become increasingly quiet.

An analysis of ice-cores, which hold a long-term record of solar activity, suggests the decline in activity is the fastest that has been seen in 10,000 years.

"It's an unusually rapid decline," explains Prof Lockwood.

Londoners enjoyed frost fairs on the Thames in the 17th Century

"We estimate that within about 40 years or so there is a 10% to 20% - nearer 20% - probability that we'll be back in Maunder Minimum conditions."

The era of solar inactivity in the 17th Century coincided with a period of bitterly cold winters in Europe.

Londoners enjoyed frost fairs on the Thames after it froze over, snow cover across the continent increased, the Baltic Sea iced over - the conditions were so harsh, some describe it as a mini-Ice Age.

And Prof Lockwood believes that this regional effect could have been in part driven by the dearth of activity on the Sun, and may happen again if our star continues to wane.

"It's a very active research topic at the present time, but we do think there is a mechanism in Europe where we should expect more cold winters when solar activity is low," he says.

He believes this local effect happens because the amount of ultraviolet light radiating from the Sun dips when solar activity is low.

This means that less UV radiation hits the stratosphere - the layer of air that sits high above the Earth. And this in turn feeds into the jet stream - the fast-flowing air current in the upper atmosphere that can drive the weather.

The results of this are dominantly felt above Europe, says Prof Lockwood.

"These are large meanders in the jet stream, and they're called blocking events because they block off the normal moist, mild winds we get from the Atlantic, and instead we get cold air being dragged down from the Arctic and from Russia," he says.

"These are what we call a cold snap... a series of three or four cold snaps in a row adds up to a cold winter. And that's quite likely what we'll see as solar activity declines."

So could this regional change in Europe have a knock-on effect on for the rest of the world's climate? And what are the implications for global warming?

In a recent report by the UN's climate panel, scientists concluded that they were 95% certain that humans were the "dominant cause" of global warming since the 1950s, and if greenhouse gases continue to rise at their current rate, then the global mean temperature could rise by as much as 4.8C.

Start Quote

This feels like a period where it's very strange... but also it stresses that we don't really understand the star that we live with”

And while some have argued that ebbs and flows in the Sun's activity are driving the climate - overriding the effect of greenhouse gas emissions, the Intergovernmental Panel on Climate Change concludes that solar variation only makes a small contribution to the Earth's climate.

Prof Lockwood says that while UV light varies with solar activity, other forms of radiation from the Sun that penetrate the troposphere (the lower layer of air that sits above the Earth) do not change that much.

He explains: "If we take all the science that we know relating to how the Sun emits heat and light and how that heat and light powers our climate system, and we look at the climate system globally, the difference that it makes even going back into Maunder Minimum conditions is very small.

"I've done a number of studies that show at the very most it might buy you about five years before you reach a certain global average temperature level. But that's not to say, on a more regional basis there aren't changes to the patterns of our weather that we'll have to get used to."

Polar lights - one manifestation of solar activity in the Earth's magnetosphere - may dim

But this weather would not be the only consequence of a drawn out period of inactivity, says Dr Green.

"If the Sun were to get very quiet, one of the few things that would happen is that we'd have very few displays of the northern lights. They are driven by solar activity, and we'd miss out on this beautiful natural phenomenon," she explains.

However, there could be positive effects too.

"Solar activity drives a whole range of space weather, and these are ultimately effects on the electricity networks, on satellites, on radio communications and GPS on your sat-nav," she explains.

And while scientists cannot discount that the random bursts of activity may still occur, calmer periods of space weather would help to maintain the technological infrastructure that we rely so heavily on.

While the full consequences of a quietening Sun are not fully understood, one thing scientists are certain about is that our star is unpredictable, and anything could happen next.

"This feels like a period where it's very strange... but also it stresses that we don't really understand the star that we live with." says Prof Harrison.

"Because it's complicated - it's a complex beast."

Solar storm

Solar storm strikes Earth following monster flare

A large coronal mass ejection has reached Earth – days after the Sun sent a massive burst of solar wind and electromagnetic radiation towards our planet. While causing no major geomagnetic storm, it has produced spectacular auroras in northern Europe.

RT.

10 January, 2014

The coronal mass ejection (CME) arrived near Earth at 2:32pm EST (7:32pm GMT) on Thursday, with its effects expected to continue throughout Friday, according to US National Oceanic and Atmospheric Administration (NOAA).

NOAA’s Space Weather Prediction Center has issued a warning of a geomagnetic storm with “minor disruptions to communications and GPS.”

While the world’s economies braced for possible blackouts in high-frequency airline and military communications, disruptions to GPS signals and power grids, enthusiasts in the northern hemisphere rushed outdoors in the hope of viewing the stunning aurora borealis as far south as Colorado.

However, American aurora spotters have been disappointed, as, according to spaceweather.com, the CME’s impact was “weaker than expected” and failed to produce widespread storms. Some frustrated Twitter users also blamed cloudy skies for not being able to see the northern lights.

Maninder Dhaliwal @dhaliwalmk

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Wow RT @EdPiotrowski: Harald Albrigsten captures the #aurora in all its glory tonight in Kvaløya, Norway.

7:22 PM - 10 Jan 2014

22 RETWEETS 12 FAVORIT

Observers were luckier around the Arctic Circle in Norway, where a dark and clear night at the time of impact, as well as more favorable latitude, put an aurora on display.

NOAA forecasters still estimated an 85 percent chance of polar geomagnetic storms before the end of Friday, and media cheered the sky watchers by saying there remains a chance of some clear aurora sightings Friday night.

The CME that stroke the Earth has been associated with the large X1.2-class solar flare that was unleashed from a giant sunspot AR1944 on January 7. The flare has been described as the most powerful this year so far, with X-class denoting the most severe intensity.

The solar phenomenon, which can send billions of tons of particles from the Sun’s atmosphere into space, is luckily not directly harmful for humans, as the Earth’s atmosphere prevents the particles from coming through. However, solar storms can affect electronic systems in satellites and on the ground, causing varying levels of disruption, and can potentially pose some danger to the astronauts orbiting the planet on board the International Space Station (ISS).

While NASA downplayed the possible impact of the current CME, saying it did not represent a threat to the ISS, the space weather concerns sparked a day-long delay of the Orbital Sciences Corp. Antares rocket launch. The rocket successfully blasted in to space on Thursday, carrying the commercial cargo ship Cygnus with supplies for the ISS crew.

Scientists are expecting more solar flares to erupt, as the Sun is currently in an active phase of its 11-year solar weather cycle. The current one, known as Solar Cycle 24, started in 2008.

Global warming

A grand solar minimum would barely make a dent in human-caused global warming

Research has shown that a grand solar minimum would offset no more than 0.3°C of global warming

the Guardian,

14 August, 2013

Recent articles in the Danish newspaper Jyllands-Posten (translation available here) and in the Irish Times both ran headlines claiming that another grand solar minimum could potentially trigger an "ice age" or "mini ice age" this century. 

These articles actually refer to the Little Ice Age (LIA) – a period about 500 to 150 years ago when global surface temperatures were approximately 1°C colder than they are today. This is quite different from an ice age, which are more like 5°C colder than today. The LIA was not actually very cold on a global scale.

So, in order to trigger another LIA, a new grand solar minimum would have to cause about 1°C cooling, plus it would have to offset the continued human-caused global warming of 1 to 5°C by 2100, depending on how our greenhouse gas emissions change over the next century.

In the Jyllands-Posten article, Henrik Svensmark (the main scientist behind the hypothesis that the sun has a significant indirect impact on global climate via galactic cosmic rays) was a bit more measured, suggesting,

"I can imagine that it will become 0.2°C colder. I would be surprised if it became 1–2°C"

So these two articles are suggesting that a grand solar minimum could have a net cooling effect in the ballpark of 1 to 6°C, depending on how human greenhouse gas emissions change over the next century. Is it plausible that a grand solar minimum could make that happen?

The short answer is, 'No.'

Fortunately, Solar Output is Stable

We're fortunate that the amount of solar radiation reaching the Earth's surface is very stable. Climate contrarians will often ask if we'd prefer if the planet were warming or cooling, suggesting that global warming is a good thing because at least the planet isn't getting colder. This is a false dichotomy - an ideal climate is a stable one.

The relatively stable climate over the past 10,000 years has allowed establishment of human civilization, by making it possible to create large stationary agricultural farms because we could rely on stable weather patterns. During that time, net global surface temperatures changes haven't exceeded 1°C from the coldest to the hottest climates, though we're now approaching that degree of change, with 1°C warming since the LIA, 0.8°C of that over the past century, with much more to come.

What difference would a grand solar minimum make in the amount of solar energy reaching Earth? Two examples are the Maunder Minimum, a period of very low solar activity between 1645 and 1715, and the Dalton Minimum, a period of low (but not as low as the Maunder Minimum) solar activity between 1790 and 1830.

400 years of sunspot observations data. Created by Robert Rohde, via Wikipedia.

Relative to current levels, the Dalton Minimum represents a 0.08% decrease in the amount of solar radiation reaching the Earth's surface, and the Maunder Minimum represents a 0.25% decline. That's how stable solar activity is. That's also why we're playing with fire by increasing the greenhouse effect so much and so quickly. We're threatening the stability of the climate that has been so favorable to our development.

Peer-Reviewed Research Says Global Warming will Continue

There have been several studies in recent years investigating what impact another grand solar minimum would have on global surface temperatures, since solar research suggests it's possible we could be due for another extended solar minimum. Generally these studies will run climate model simulations under a given greenhouse gas emissions scenario with stable solar activity, then run the same scenario with the sun going into a grand minimum, and look at the difference in resulting global surface temperature changes.

Using this approach, Feulner & Rahmstorf (2010) (PDF available here) estimated that another solar minimum equivalent to the Dalton and Maunder minima would cause 0.09°C and 0.26°C cooling, respectively.

The global mean temperature difference is shown for the time period 1900 to 2100 for the IPCC A2 emissions scenario. The red line shows predicted temperature change for the current level of solar activity, the blue line shows predicted temperature change for solar activity at the much lower level of the Maunder Minimum, and the black line shows observed temperatures through 2010. Adapted from Feulner & Rahmstorf (2010) by SkepticalScience.com

Jones et al. (2012) (PDF available here) arrived at a nearly identical result, with cooling from another Dalton and Maunder minimum at 0.09°C and 0.26°C, respectively. Similarly, a new paper by Anet et al. (2013) found that a grand solar minimum will cause no more than 0.3°C cooling over the 21st century.

Consistent with these previous studies, Meehl et al. (2013) (PDF available here) estimate a Maunder Minimum would cause about 0.26°C cooling, but as soon as solar activity began to rise again, that cooling would be offset by solar warming. This is a key point, because a grand solar minimum would not be a permanent change. These solar minima last for a few decades, but eventually solar activity rises once again. Thus any cooling caused by a solar minimum would only be temporary.

The cooling effect of a grand solar minimum can also be estimated very easily without the aid of climate models, because the change in the amount of solar radiation reaching the Earth's surface is directly proportional to the temperature change it causes. Performing this calculation yields the same result as the model-based research: approximately 0.3°C cooling from another Maunder-type grand solar minimum. Click here to see the details behind the calculation.

The Heating of the Deep Oceans

In the Jyllands-Posten article, Svensmark also disputes the data showing the accelerated accumulation of heat in the deep oceans.

"How can the ocean below 700 meters be heated up, without the upper ocean warming up accordingly?"

This is an increasingly common argument made by climate contrarians, and a bit of a strange one. The data are what they are - we've measured the deep ocean warming, including with reliable instruments on Argo buoys for close to a decade now. Even if we couldn't explain how the heat got there, it's there.

5-year averages of ocean heat content 0-700 meters (red) and 0-2000 meters (black), from the National Oceanographic Data Center

But let's address the question anyway - do we expect to have seen some obvious indication of heat being transferred from the shallow to deep ocean layers?

It's certainly not clear that we should. Consider the analogy of a bathtub. Water from the faucet represents heat entering the shallow ocean layer. Water exiting the drain represents heat leaving the shallow oceans and entering the deep oceans. The water level in the bathtub represents the heat in the shallow ocean layer (which is what we measure).

If the amount of water entering the tub from the faucet is the same as the amount of water draining out of the tub, the water level in the tub won't change. Yet the water still flows down the drain. Climate scientist Gavin Schmidt has discussed this point, summarized here.

In short, we wouldn't necessarily see the heat being transferred through the shallow to the deep oceans. However, there has been plenty of warming of the shallow oceans that could have been transferred to the deeper oceans. In our case, the water is flowing into the tub faster than it's draining out - the shallow oceans are warming fast, as the figure above illustrates.

Svensmark Gets Ocean Warming Wrong

Unfortunately Svensmark appears to be unfamiliar with this ocean heating data, saying,

"The thousands of buoys that we have deployed after 2003 to measure the ocean temperature, have not registered any temperature rise."

This is just totally wrong, even if we ignore the rapid warming of the deep oceans (as is clear from a simple examination of the figure above). The ocean heat content data can be downloaded from the National Oceanographic Data Center here. The heating trend since 2003 in the upper 700 meters of oceans is equivalent to nearly 1 Hiroshima atomic bomb detonation per second (plus another 3 per second in the deep oceans). Both the shallow and deep oceans are accumulating a whole lot of heat, with no signs of slowing whatsoever. If anything, the heating of the oceans and the planet as a whole is accelerating.

Human Influence on Climate Change is Bigger than the Sun's

The bottom line is that the sun and the amount of solar radiation reaching Earth are very stable. Even during the Maunder and Dalton grand solar minima, global cooling was relatively small - smaller than the amount of global warming caused by human greenhouse gas emissions over the past century.

A new grand solar minimum would not trigger another LIA; in fact, the maximum 0.3°C cooling would barely make a dent in the human-caused global warming over the next century. While it would be enough to offset to about a decade's worth of human-caused warming, it's also important to bear in mind that any solar cooling would only be temporary, until the end of the solar minimum.

The science is quite clear that the human influence on climate change has become bigger than the sun's. At this point, speculation about another mini ice age is pure fantasy